The present invention relates to a layered plastic web, particularly adapted for attachment through heat and pressure to fabric.
For many years, the attachment of cloth numerals and/or other identifying information on athletic attire, was made by stitching. For less demanding conditions, including casual sportswear, logos and the like were either attached to the garment by stitching or applied by silk screening.
More recently, the development of thermoplastic films, such as vinyl and polyurethane, has progressed to the point where lettering can be attached directly to the fabric, by the application of heat and pressure. Once attached, the thermoplastic letters retain sufficient flexibility to resist embrittlement and cracking, without separating from the fabric during washing and drying.
The conventional procedure typically includes stacking a plurality of sheets of lettering web material. A die or other cutting means such as a water knife, cuts through the plurality of sheets simultaneously, forming distinct letters or numbers. Thus, a stack of sheets, when cut, may produce dozens of identical characters, for example, the letter "A". In a similar fashion, other stacks of sheets are cut with the characters "B", "C". . . "1". . . "9", etc. Packages of the characters are provided to the athletic lettering retailers, who can arrange particular letters, for example, the name of a player, on a jersey and, by the application of heat and pressure on each letter individually, or on all the letters as arranged on the jersey, attach them to the fabric.
U.S. Pat. No. 3,660,212, issued to Liebe, Jr. on May 2, 1972, discloses one type of material for athletic lettering. The material of the Liebe patent has two layers of polyvinylchloride bonded to each other. Furthermore, one of the layers of polyvinyl- chloride is releasably adhered to a release coated paper sheet. During application on fabric, the cut lettering material of the Liebe patent requires the release sheet backing, to which heat is applied for causing the material to adhere to the fabric of the uniform. This adhering of the lettering material of the Liebe patent to the material of the sport uniform is a mechanical bonding. This is due to the lettering material sinking into the material of the sport uniform and encapsulating the fabric. This type of web can be referred to as an "adhesive up" web, because the top surface of the web prior to cutting, ultimately adheres to the fabric.
A variation of the vinyl lettering described in the Liebe patent, is marketed by Stahls, Inc. of St. Clair Shores, Michigan, and consists of a release coated paper carrier sheet, on which a pigmented, stretch vinyl layer has been applied by casting (i.e., solution coating). A top layer of adhesive is carried on the vinyl, i.e., as an "adhesive up" lettering system.
Vinyl lettering exhibits a number of disadvantages, as mentioned, for example, in Stahls, Encyclopedia of Heat Applied Lettering, Second Edition, Version 2.1 (Library of Congress Registration TXU133-924). The vinyl material itself, has relatively low tensile strength and tear resistance, requiring the use of a relatively thick vinyl letter. Vinyl has relatively low flexibility, which becomes even worse as temperature decreases. The extra weight and inflexibility of large vinyl lettering on athletic jerseys, represents a significant disadvantage. Moreover, vinyl does not resist abrasion, which is another disadvantage in athletic attire as well as casual attire worn for vigorous activities. For example, on the well known Taber test for abrasion resistance, vinyl material is abraded at the rate of 178 mg. This compares poorly with other material such as nylon (44 mg), or urethane (3 mg).
Another disadvantage of the vinyl coated release paper for lettering purposes, arises from the fact that the carrier sheet is release-coated on only one side, with the result that the penetration of moisture from the other side induces curling of the paper. This curling can stress the vinyl such that it, too, has a tendency to curl onto itself.
When such vinyl letters are die cut and stored for a period of time, curling can become a significant problem when the end user attempts to carefully place the cut numerals precisely on the desired location on the fabric. Moreover, the release coating on the paper may not be uniform, with the result that any overlap of the paper over the edges of the vinyl letter, tends to stick to the fabric during the application of heat and pressure through the carrier sheet.
These disadvantages of vinyl lettering, particularly the tendency to curl with the resulting separation of the vinyl material from the carrier sheet, renders vinyl ill-suited for small letters. Known vinyl-based webs for athletic lettering, are not amenable to precision cutting of complex logos or small lettering, as by the use of a computer controlled cutting blade. The susceptibility of the vinyl web to curling, coupled with the rather low peel value of less than 5 ounces between the vinyl and the release-coated sheet, would result in lateral movement of the vinyl on the release sheet adjacent the cutting edge of the blade (which travels horizontally through the web). The edges of the letters would therefore not be cut cleanly, and the resulting shear forces coupled with the inherent tendency of the paper and/or vinyl to curl, would result in the cut letters lifting from the carrier sheet during the cutting operation.
A related disadvantage in the use of vinyl letters, is that in order to achieve satisfactory opacity, the vinyl material must be relatively thick. Nevertheless, commercially available vinyl webs for athletic lettering, typically come with a warning not to apply them to fabrics which have a pattern, for example, a pin-striped baseball jersey. The chance of "strike through" is especially critical with fabric of this type. Moreover, users are typically warned to store the inventory away from heat, and the lettered garments are not to be dry cleaned.
As described in Stahls' Encyclopedia, keeping letters aligned before application has always been a problem. When vinyl letters have been applied and a mistake is discovered, the garment must either be repaired or discarded. Repair of misapplied vinyl letters, typically require considerably physical effort, the use of foul-smelling toxic solvents, and the dirtying of one's hands. Solvents typically used for repair purposes, are either extremely flammable, caustic, or poisonous. The use of vinyl lettering is prone to mistakes, in part due to alignment problems inherent in the placement of individually die cut letters on the garment, e.g., curling or static electricity makes the letters "jump" when a cover sheet, heat resistant tape, or platen come near by.
Because of the disadvantages associated with vinyl, polyurethane has recently been recognized as a superior but more expensive material for athletic lettering. Although the performance of urethane lettering is superior to that of vinyl, urethane materials are more difficult to apply. This is due in part to the difficulty in preparing a satisfactory urethane laminate web which includes layers that exhibit significantly different coefficients of thermal expansion, or elasticity. The advantages of urethane relative to vinyl, however, are overwhelming. Urethane has at least twice the tensile strength, tear resistance, and elongation capability, relative to vinyl. The flexibility of urethane is maintained at low temperatures. The abrasion resistance, as noted above, is far superior.
U.S. Pat. Nos. 4,269,885 and 4,423,106, issued May 26, 1981 and Dec. 27, 1983 to Mahn, disclose a laminated web consisting essentially of two films, preferably a polyester adhesive bonded to a die-extruded polyurethane lettering layer. After characters are cut out of the web, the polyester adhesive layer is placed against the fabric, a paper cover is placed over the polyurethane layer, and heat and pressure are applied. The melting point of the polyester adhesive is lower than that of the polyurethane, so that the polyester melts into the fabric.
It may be possible that, if the release coated paper carrier sheet used during fabrication of the laminate is retained, a somewhat more complex graphic pattern, for example, a team emblem or logo, can be cut, using programmable cutting equipment. This would, however, be considered an "adhesive down" web, because the polyester adhesive surface which ultimately adheres to the fabric, is hidden between the release coasted carrier sheet and the polyurethane letter material.
Significant problems, however, are presented to anyone who cuts elastomeric letters from the Mahn web, by computer. For example, the presence of a release coating on the carrier sheet prevents the precise cutting of the polyurethane layer. This is in large part a result of the flexibility of the polyurethane, and the softness of the polyester adhesive between the polyurethane and carrier sheet. Unless great care is taken, sharp corners and edges cannot be preserved on the cut web. The adhesive between the polyurethane and carrier sheet, thus presents a practical size limitation on the lettering, i.e., small, precise letters and designs cannot be cut due to the excessive flexibility of the polyurethane and underlying adhesive as the knife makes corner cuts. This relationship between the adhesive and the cutting impression, especially at the corners, makes weeding away the unwanted portion of the web very difficult.
Thus, despite recent advances in the state of the art, the current technology represented by the transfer of elastomeric, thermoplastic lettering by the application of heat and pressure suffers from significant disadvantages.